The present invention is related to a pneumatic tool, and more particularly to an improved airflow controlling mechanism.
FIGS. 1 and 2 show a conventional controlling mechanism of a pneumatic tool for controlling airflow direction and amount. A controlling disc 3 is coaxially accommodated in an extension air chamber 2 of a cylinder 1. One face of the controlling disc 3 abuts against a wall of the close end of the air chamber 2. The wall of the air chamber 2 is formed with two directional vents 4. The bottom of the annular wall of the air chamber 2 is formed with an inlet 5 for communicating with external air source. The controlling disc 3 is formed with a radial air passage 6. Two ends of the air passage 6 respectively communicate with the inlet 5 and a corresponding directional vent 4, whereby the external high pressure air is conducted from the inlet 5 through the air passage 6 and the directional vent 4 into the air chamber of the other end of the cylinder 1. Accordingly, the rotational direction of the pneumatic tool can be controlled. Moreover, by means of changing the amount of the airflow, the rotational speed of the pneumatic tool can be adjusted.
In the above conventional controlling mechanism of the pneumatic tool, the face of the controlling disc 3 abuts against the close end of the extension air chamber 2 to restrict the airflow from escaping. However, this can hardly achieve an optimal airtight effect. As a result, leakage often takes place in the conventional pneumatic tool to affect the operation thereof. In the case that the face of the controlling disc and the close end of the extension air chamber are manufactured at higher precision for achieving better airtight state, the manufacturing cost will be greatly increased and the airtight effect still cannot be ensured.